Stack seat with vertical back



FIG. 1 is a perspective view thereof;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a right side view thereof, left side view being a mirror imagethereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof.

The ornamental design for a stack seat with vertical back, as shown anddescribed.